FR3109195A1 - Underwater pipe comprising an internal sealing sheath - Google Patents

Abstract

Subsea pipe comprising an internal polyamide sealing sheath The application relates to a subsea pipe intended for the transport of hydrocarbons and/or gas comprising a layer of metal reinforcement around a single-layer internal polymeric sealing sheath comprising a semi-aromatic semi-crystalline polyamide, its method of preparation and the use of a semi-aromatic semi-crystalline polyamide for improving the stress corrosion of said underwater pipe. Figure for abstract: 1

Description

Underwater pipe comprising an internal sealing sheath

polyamide

The present invention relates to an underwater pipe intended for the transport of hydrocarbons in deep water or for the transport of gas, typically the transport of CO ₂ .

These pipes are capable of being used at high pressures, greater than 100 bars, or even up to 1000 bars, and at high temperatures, greater than 130 ° C, or even 170 ° C, for long periods of time, that is, that is to say several years, typically 20 years.

Submarine pipes intended for the transport of hydrocarbons or gases in deep water generally comprise at least one metallic reinforcing layer around an internal polymeric sealing sheath, in which the hydrocarbons or gases circulate.

The material constituting the polymeric internal sealing sheath must be chemically stable and capable of mechanically withstanding the fluid transported and its characteristics (composition, temperature and pressure). The material must combine characteristics of ductility, resistance to time (generally the pipe must have a service life of at least 20 years), mechanical resistance, heat and pressure. The material must in particular be chemically inert with respect to the chemical compounds constituting the transported fluid or have an aging whose kinetics are compatible with the application. Typically, the hydrocarbons transported include crude oil, water, and pressurized gases, such as hydrogen sulphide (H ₂ S) in a concentration generally of the order of 100 ppm, carbon dioxide (CO ₂ ) at a pressure of up to 100 bars (such pressures being achievable for certain underwater wells extracting oil from pre-salt deposits) and methane (CH ₄ ) generally at a pressure of between 1 bar and several hundred bars . Petroleum can also contain organic acids, such as benzoic acid, methanoic acid and / or acetic acid. They increase the acidity of crude oil (between 0.1 and 8 TAN for example). This acidity can lead to the premature degradation of certain polymers, such as polyamides.

Typically, gas transport pipes, and more particularly gas injection pipes, mainly transport CO ₂ .

Various polymeric materials are used in the internal polymeric sealing sheath of an underwater flexible pipe, for example:

- polyethylene, in particular high density polyethylene, for low temperature applications (typically below 90 ° C). Polyethylene is however sensitive to the phenomenon of blistering under certain conditions.

- polyamide (PA), in particular polyamide 11. Unlike polyethylene, polyamide has good resistance to blistering when it is pressurized and at temperature, as well as a low tendency to swell when in contact with the petroleum fluid. Polyamide is generally used for conditions of transporting hydrocarbons for which the pressure is high and where the temperature preferably remains below 90 ° C, or even for a temperature which can rise up to 110 ° C.

On the other hand, one of the disadvantages of polyamide is that it tends to hydrolyze in the presence of water, often contained in crude products (chemical aging). Hydrolysis is rapid when subjected to temperatures (on the order of 110 ° C and above) and low pH values (pH below 7). Another drawback is its purchase cost, which is significantly higher than that of polyethylene.

- polyvinylidene fluoride (PVDF) has very good chemical inertness. PVDF-based conduits can withstand high operating pressures as well as temperatures up to 130 ° C-150 ° C.

Its major drawback remains its price, which is much higher than that of polyethylene or polyamide.

The use of thermoplastic materials in unbound flexible pipes is summarized in normative documents API RP 17B (2014) and API 17J (2014) published by the American Petroleum Institute.

The development of an alternative internal sealing polymeric sheath with properties compatible with their use in contact with high temperature hydrocarbons (low swelling, low sensitivity to cavitation, good mechanical resistance, in particular to creep, etc., good chemical resistance to the components of hydrocarbons), and in particular in contact with hydrocarbons having a partial pressure of CO₂ high (more than 5 bars) is desired.

Application US 2013/0032240 describes an underwater flexible pipe intended for the transport of fluids comprising a multi-layer internal sealing polymeric sheath, a first layer being in polyolefin, in polyamide or in PVDF and a second layer being in polyarylene ether ketone, in poly (phenylene sulfide) (PPS), in a polyarylene-ether-ketone (PAEK) / PPS mixture, in polyphenylsulfone (PPSU), or in poly (alkylene naphthalate). However, multilayers as an internal sheath have the disadvantage that gases accumulate at the interface between the layers, which deteriorates them and degrades the properties of the polymeric internal sealing sheath.

As the pipes are used at great depth, it is necessary that their at least one metallic reinforcing layer, responsible for taking up the radial circumferential pressure forces and the longitudinal tensile forces, have excellent mechanical characteristics. Now generally, in the case where these metallic reinforcement layers are made of steel, carbon steel or low alloy, the increase in mechanical characteristics is done to the detriment of resistance to stress corrosion, which makes it difficult to update. point of a flexible pipe intended to operate at very great depths, 2000m and more, and capable of withstanding very corrosive hydrocarbons. The corrosive hydrocarbons targeted are in particular multiphase hydrocarbons comprising high partial pressures of H ₂ S, typically 0.5 bar to 5 bar, and / or of CO ₂ , typically at least 5 bar. Such fluids are generally very acidic, typically their pH is less than 4.5. In addition, their temperature can exceed 60 ° C (operating temperature), or even 90 ° C (design temperature).

The pipes include at least one layer of metallic reinforcement which is subject to stress corrosion cracking (SCC). In fact, under the conditions of use of the pipe, the at least one metallic reinforcing layer is subjected to very high radial pressure or longitudinal tension stresses and it is in a very corrosive environment, in particular in the presence of CO ₂ and H ₂ S. Stress corrosion causes the appearance of cracks and degrades the at least one reinforcing layer.

One of the objectives of the present invention is to provide an underwater pipe for the transport of hydrocarbons and / or gas (in particular CO ₂ ), the stress corrosion of which is minimized.

To this end, according to a first object, the invention relates to an underwater pipe intended for the transport of hydrocarbons and / or gas comprising a metal reinforcing layer around a single-layer internal polymeric sealing sheath comprising a semi-crystalline semi-aromatic polyamide including:

- at least 60% by moles of the units derived from diamines are derived from one or more diamines chosen from aliphatic, cycloaliphatic or alkylaromatic diamines having a number of carbons from 8 to 22, and

- at least 65% by moles of the units obtained from dicarboxylic acids are obtained from one or more aromatic dicarboxylic acids,

the internal polymeric sealing sheath being the single polymeric layer within the metallic reinforcement layer.

The term "transport of oil and / or gas" means the transport of oil, gas or a mixture thereof.

A semi-crystalline polyamide, within the meaning of the invention, denotes a polyamide which has a melting point (Tm) in differential scanning calorimetry (“Differential scanning calorimetry” (DSC) in English) DSC according to the ISO 11357-3 standard. of 2018, and an enthalpy of crystallization during the cooling step at a speed of 20K / min in DSC measured according to the ISO 11357-3 standard of 2018 greater than 30 J / g, preferably greater than 40 J / g.

Preferably, the polyamide as defined above of the internal polymeric sealing sheath of the pipe has a melting temperature (considering the peak corresponding to the highest melting temperature in DSC according to ISO 11357-3 of 2018 ) less than 330 ° C, especially less than 300 ° C, preferably less than 280 ° C. Such melting temperatures facilitate the preparation of the liner by extrusion.

Preferably, the polyamide as defined above of the internal polymeric sealing sheath of the pipe has an elongation at break at 20 ° C according to ISO 527-2 of 2012 greater than 20%, preferably greater than 40% , preferably greater than 50%.

Preferably, the polyamide as defined above of the internal polymeric pipe sealing sheath has a retention of tensile strength of at least 50% when aged 90 days at 100 ° C in the pipe. water at pH 6 according to the API TR 17TR2 standard of 2003.

Preferably, the polyamide as defined above of the internal polymeric sealing sheath of the pipe resists the blistering phenomenon at a pressure of 500 bars of CO ₂ and a temperature of 100 ° C, resistance to the blistering phenomenon. being evaluated according to API 17J of 2014.

Preferably, the polyamide as defined above of the internal polymeric sealing sheath of the pipe has a melt index measured at 340 ° C under a mass of 5.0 kg according to ISO. 1133-1 from 2011 less than 2.0 g / 10 min, in particular less than 10.0 g / 10 min.

At least 60% by moles, in particular at least 75% by moles, preferably at least 90% by moles, more preferably at least 95% by moles, or even all (100%) of the units derived from diamines of the polyamide of the sheath Internal sealing polymer for the pipe are obtained from one or more diamines chosen from aliphatic, cycloaliphatic or alkylaromatic diamines having a number of carbons from 8 to 22, in particular from 9 to 22, preferably from 10 to 22. These proportions molars are relative to the total number of units derived from polyamide diamines.

When the diamine is aliphatic, it can be linear or branched.

When the aliphatic diamine is linear, it has the formula H ₂ N- (CH ₂ ) _a -NH ₂ , a being an integer from 8 to 22, in particular from 9 to 22, preferably from 10 to 22.

Preferably, when the diamine is linear aliphatic and has from 10 to 22 carbon atoms, it is chosen from decanediamine (a = 10), undecanediamine (a = 11), dodecanediamine (a = 12), tridecanediamine ( a = 13), tetradecanediamine (a = 14), hexadecanediamine (a = 16), octadecanediamine (a = 18), eicosanediamine (a = 20), docosanediamine (a = 22) and diamines obtained from fatty acids. Preferably, when the diamine is linear aliphatic and has from 9 to 22 carbon atoms, it is chosen from the above list, to which is added nonanediamine (a = 9). Preferably, when the diamine is linear aliphatic and has from 8 to 22 carbon atoms, it is chosen from the above list, to which octanediamine (a = 8) and nonanediamine (a = 9) are added.

When the aliphatic diamine is branched and has from 10 to 22 carbon atoms, it is preferably chosen from 2,4-diethyl-1,6-hexanediamine, 1,3-dimethyl-1,8-octanediamine, 1 , 4-dimethyl-1,8-octanediamine, 2,2-dimethyl-1,8-octanediamine, 2,4-dimethyl-1,8-octanediamine, 3,3-dimethyl-1,8-octanediamine, 3,4-dimethyl-1,8-octanediamine, 4,4-dimethyl-1,8-octanediamine, 4,5-dimethyl-1,8-octanediamine, 5-methyl-1,9-nonanediamine, 2-butyl-1,8-octanediamine and 3-butyl-1,8-octanediamine. Preferably, when the diamine is branched aliphatic and has from 8 to 22 carbon atoms or from 9 to 22 carbon atoms, it is chosen from the above list, to which 2,2,4-trimethyl-1 are added. , 6-hexanediamine, 2,4,4-trimethyl-1,6-hexanediamine, 2,2-dimethyl-heptanediamine, 2,3-dimethyl-heptanediamine, 2,4-dimethyl-heptanediamine, 2, 5-dimethyl-heptanediamine, 2-methyl-1,8-octanediamine, 3-methyl-1,8-octanediamine, 4-methyl-1,8-octanediamine.

When the diamine is cycloaliphatic, it is preferably chosen from those comprising one or two rings.

The cycloaliphatic diamine comprising a ring and having from 10 to 22 carbon atoms is in particular 5-amino-1,3,3-trimethylcyclohexanemethylamine, bis (aminopropyl) piperazine or. The cycloaliphatic diamine comprising a ring and having from 9 to 22 carbon atoms is in particular chosen from the above list to which is added 5-amino-2,2,4-trimethyl-1-cyclopentanemethylamine. The cycloaliphatic diamine comprising a ring and having from 8 to 22 carbon atoms is in particular chosen from the above list to which are added 5-amino-2,2,4-trimethyl-1-cyclopentanemethylamine, 1,3- cyclohexanedimethylamine, 1,4-cyclohexanedimethylamine and bis (aminoethyl) piperazine.

The cycloaliphatic diamine comprising two rings corresponds in particular to the following general formula:

in which :

- R ₁ , R ₂ , R ₃ and R ₄ independently represent a group chosen from a hydrogen atom or an alkyl of 1 to 6 carbon atoms, and

- X represents either a single bond or a divalent group consisting of:

- a linear or branched aliphatic chain comprising from 1 to 10 carbon atoms, optionally substituted by cycloaliphatic or aromatic groups of 6 to 8 carbon atoms, or

- a cycloaliphatic group of 6 to 12 carbon atoms.

More preferably, the cycloaliphatic diamine is chosen from bis (4-aminocyclohexyl) methane, bis (3-methyl-4-aminocyclohexyl) propane, bis (3,5-dialkyl-4-aminocyclohexyl) methane, bis (3 , 5-dialkyl-4-aminocyclohexyl) ethane, bis (3,5-dialkyl-4-aminocyclohexyl) propane, bis (3,5-dialkyl-4-aminocyclo-hexyl) butane, bis- (3-methyl -4-aminocyclohexyl) -methane (denoted BMACM, MACM or B), p-bis (aminocyclohexyl) -methane (PACM) and bis (aminocyclohexyl) propane (PACP) (2,2-bis (4-aminocyclohexyl) propane ).

A non-exhaustive list of these cycloaliphatic diamines is given in the publication “Cycloaliphatic Amines” (Encyclopaedia of Chemical Technology, Kirk-Othmer, 4th Edition (1992), pp. 386-405).

2,5-bis-aminoethyl-p-xylene is an example of an alkylaromatic diamine having 9 to 22 or 10 to 22 carbon atoms. The alkylaromatic diamine having from 8 to 22 carbon atoms is in particular chosen from 2,5-bis-aminoethyl-p-xylene, 1,3-xylylenediamine (also called m-xylylenediamine and denoted MXD or MXDA) and 1 , 4-xylylene diamine.

The units derived from diamines having 10 to 22 preferred carbon atoms of the polyamide are derived from one or more diamines selected from 1,12-dodecanediamine and 1,18 octa-decanediamine. The units derived from diamines having 9 to 22 preferred polyamide carbon atoms are derived from one or more diamines chosen from the above list, to which are added 1,9-nonanediamine and 2-methyl-1, 8-octanediamine. The units derived from diamines having 8 to 22 preferred carbon atoms of the polyamide are derived from one or more diamines chosen from the above list, to which are added 1,3-xylylenediamine, 1,9-nonanediamine and 2-methyl-1,8-octanediamine.

At most 40% by moles, in particular at most 25% by moles, preferably at most 10% by moles, more preferably at most 5% by moles of the units derived from diamines of the polyamide of the internal polymeric sealing sheath of the pipe are units derived from other diamines, that is to say from diamines which are not aliphatic, cycloaliphatic or alkylaromatic diamines having a carbon number of 8 to 22.

Among these other diamines can be cited:

- diamines comprising more than 22 carbon atoms,

- linear aliphatic diamines comprising less than 8 carbon atoms such as ethylenediamine (a = 2), propylenediamine (a = 3), butanediamine (a = 4), pentanediamine (a = 5), hexanediamine (a = 6), heptanediamine (a = 7),

- branched aliphatic diamines comprising less than 8 carbon atoms such as 2-methyl-1,5-pentanediamine and 3-methyl-1,5-pentanediamine,

- cycloaliphatic diamines comprising less than 8 carbon atoms such as 1,3-cyclohexanediamine and 1,4-cyclohexanediamine,

- alkylaromatic diamines comprising less than 8 carbon atoms,

- aromatic diamines (regardless of their number of carbon atoms) such as para-phenylenediamine, meta-phenylenediamine, 1,4-naphthalenedimethylamine, 1,5-naphthalenedimethylamine, 2,6-naphthalenedimethylamine, 2,7-naphthalenedimethylamine, 4,4'-diaminodiphenylsulfone and 4,4'-diaminodiphenyl ether.

When the semi-crystalline semi-aromatic polyamide has at least 60 mol% of the units derived from diamines derived from one or more diamines chosen from aliphatic, cycloaliphatic or alkylaromatic diamines having a number of carbons from 9 to 22, the most 40 mol% of the units derived from other diamines can be derived from aliphatic, cycloaliphatic or alkylaromatic diamines having 8 carbon atoms, in addition to those listed above. For example, octanediamine is then another diamine.

When the semi-crystalline semi-aromatic polyamide has at least 60 mol% of the units derived from diamines derived from one or more diamines chosen from aliphatic, cycloaliphatic or alkylaromatic diamines having a number of carbons from 10 to 22, the most 40 mol% of the units derived from other diamines can be derived from aliphatic, cycloaliphatic or alkylaromatic diamines having 8 or 9 carbon atoms, in addition to those listed above. For example, octanediamine and nonanediamine are then other diamines.

At least 65% by moles, in particular at least 75% by moles, preferably at least 90% by moles, more preferably at least 95% by moles, or even all (100%) of the units derived from dicarboxylic acids of the polyamide of the Internal polymeric sealing sheath of the pipe are obtained from one or more aromatic dicarboxylic acids. These molar proportions are relative to the totality of units derived from aromatic dicarboxylic acids of the polyamide.

These aromatic dicarboxylic acids are typically phthalic acid, terephthalic acid (denoted T), isophthalic acid (denoted I), naphthalenic diacid, 1,3-phenylenedioxydiacetic acid, 1,4-phenylenedioxydiacetic acid, diphenic acid, 4,4'-oxidibenzoic acid, diphenylmethane-4,4'-dicarboxylic acid, diphenylethane-4,4'-dicarboxylic acid, diphenylpropane-4,4'-dicarboxylic acid , diphenylsulfone-4,4'-dicarboxylic acid, 4,4'-biphenyldicarboxylic acid, especially phthalic acid, terephthalic acid, isophthalic acid and naphthalenic diacid, preferably phthalic acid, terephthalic acid, isophthalic acid, particularly preferably terephthalic acid and isophthalic acid. In the latter case, the polyamide is then generally called polyphthalamide (PPA). Particularly preferably, these aromatic dicarboxylic acids are terephthalic acid.

At most 35% by moles, in particular at most 25% by moles, preferably at most 10% by moles, more preferably at most 5% by moles of the units derived from dicarboxylic acids of the polyamide of the internal polymeric sealing sheath of the conducted are units derived from other dicarboxylic acids, that is to say non-aromatic.

These non-aromatic dicarboxylic acids can be aliphatic dicarboxylic acids (linear, branched and / or cyclic), such as:

- linear aliphatic dicarboxylic acids chosen from malonic acid (b = 3), succinic acid (b = 4), pentanedioic acid (b = 5), adipic acid (b = 6), l ' heptanedioic acid (b = 7), octanedioic acid (b = 8), azelaic acid (b = 9), sebacic acid (b = 10), undecanedioic acid (b = 11), dodecanedioic acid (b = 12), brassylic acid (b = 13), tetradecanedioic acid (b = 14), hexadecanedioic acid (b = 16), octadecanoic acid (b = 18), octadecenedioic acid (b = 18), eicosanedioic acid (b = 20), docosanedioic acid (b = 22) and fatty acid dimers containing 36 carbons,

- branched aliphatic dicarboxylic acids chosen from dimethylmalonic acid, 2-methyladipic acid, 2,2,4-trimethyladipic acid, 2,4,4-trimethyladipic acid, 2,2-dimethylglutaric acid , 2,2-diethylsuccinic acid,

- dicarboxylic acids cycloaliphatic acids chosen from cyclopentane 1-3-dicarboxylic acid, cyclohexane 1,3-dicarboxylic acid and cyclohexane 1,4-dicarboxylic acid.

The polyamide of the single-layer internal polymeric pipe seal can be a homopolymer, a copolymer, a terpolymer or a mixture thereof.

In addition to units derived from diamines and dicarboxylic acids, the polyamide may include units derived from amino acid and / or lactam.

The polyamide can for example comprise at least one unit resulting from an amino acid chosen from 9-aminononanoic acid, 10-aminodecanoic acid, 12-aminododecanoic acid and 11-aminoundecanoic acid as well as its derivatives, in particular N-heptyl-11-aminoundecanoic acid.

The polyamide can for example comprise at least one unit resulting from a lactam chosen from pyrrolidinone, piperidinone, caprolactam, enantholactam, caprylolactam, pelargolactam, decanolactam, undecanolactam, and laurolactam.

Preferably, the internal polymeric single-layer sealing sheath of the pipe comprises, as semi-crystalline semi-aromatic polyamide, PA9T, PA12T, PA18T or a mixture thereof, PA9T being particularly preferred.

The nomenclature used to define polyamides is described in standard ISO 16396-1: 2015 "Plastics - Polyamide (PA) materials for molding and extrusion - Part 1: Designation system, product marking and basis for specification".

Examples of usable PA9Ts are GENESTAR ™ PA9T from Kuraray or Ultramid® advanced N4H from BASF. Vestamid HT plus grade M3000 or M8000 from Evonik or Grivory HT3 from EMS-Grivory are suitable PA10T-based polyamides.

When the at least 60% by moles of units derived from diamines of the semi-crystalline semi-aromatic polyamide are derived from one or more diamines having a number of carbons of 10 to 22, the single-layer internal polymeric sealing sheath of the The conduit preferably comprises, as semi-crystalline semi-aromatic polyamide, PA12T, PA18T or a mixture thereof.

Thanks to their barrier effect to gases liable to damage the metallic reinforcement layer (H ₂ S and / or CO ₂ ), the polyamides defined above make it possible to improve the resistance of the pipe by reducing the composition of the annulus. , and in particular to improve the resistance to stress corrosion of the at least one metallic reinforcing layer, and therefore the service life of the pipe. Stress corrosion can be assessed by NACE standard TM0177-2016-SG.

Advantageously, these polyamides are more resistant to hydrolysis than PA11 or PA12.

The internal polymeric sealing sheath comprising the polyamide defined above typically comprises:

- a polymer matrix, and

- optionally components dispersed discontinuously in the polymer matrix.

By "polymeric matrix" is meant the continuous polymeric phase which forms the internal polymeric sealing sheath. The polymeric matrix is a continuous matrix. The internal polymeric sealing sheath may optionally include components dispersed discontinuously in the polymeric matrix, but which are not part of the polymeric matrix. Such components can for example be fillers such as fibers.

The polymeric matrix of the internal polymeric sealing sheath is generally obtained by extruding one or more polymers (which will form the polymeric matrix) and optionally additives (masterbatch). During extrusion, some additives are incorporated into the polymeric matrix, while others do not mix with the polymers forming the polymeric matrix and disperse discontinuously in the polymeric matrix, to form discontinuously dispersed components. in the polymer matrix.

According to a first alternative, the pipe comprises an internal polymeric sealing sheath, the polymeric matrix of which comprises a polyamide as defined above.

According to this alternative, the internal polymeric sealing sheath, the polymeric matrix of which comprises the polyamide, is generally obtained by extrusion of one or more polymers (which will form the polymeric matrix), at least one of them being the polyamide defined above, and optionally in the presence of additives.

The components dispersed discontinuously in the polymer matrix can optionally comprise polymers, for example a polyamide as defined above. However, a pipe:

- comprising a polymeric sealing sheath comprising a component dispersed discontinuously in the polymer matrix (in particular fillers such as fibers) comprising or consisting of a polyamide as defined above,

- but whose polymer matrix is free of polyamide as defined above,

does not meet the definition of a pipe comprising at least one polymeric sealing sheath, the polymeric matrix of which comprises a polyamide as defined above, as defined in this first alternative.

According to a second alternative, the pipe according to the invention comprises an internal polymeric sealing sheath comprising a component dispersed discontinuously in the polymer matrix, said component comprising a polyamide as defined above.

According to this second alternative, a component dispersed discontinuously in the polymer matrix of the internal polymeric sealing sheath comprises a polyamide as defined above. The component can be a filler such as a fiber. The component comprising a polyamide as defined above is generally one of the additives of the masterbatch used during the extrusion. According to this second alternative, the polymeric matrix of the internal polymeric sealing sheath may be free from polyamide as defined above.

According to a third alternative, the pipe according to the invention comprises an internal polymeric sealing sheath comprising a component dispersed discontinuously in the polymeric matrix, said component comprising a polyamide as defined above and the polymeric matrix of which comprises a polyamide. as defined above.

According to this third alternative, the polyamide as defined above is therefore present both in the polymeric matrix and in a component dispersed discontinuously in the polymeric matrix.

The internal polymeric sealing sheath preferably comprises at least 50% by weight, in particular at least 65% by weight, preferably at least 75% by weight, particularly preferably at least 85% by weight of polyamide as defined herein. above with respect to the internal polymeric sealing sheath.

The internal polymeric sealing sheath can also include a plasticizer, which can improve the performance of the cold sheath (thanks to the lowering of the glass transition temperature by 10 ° C, or even 25 ° C, measurable by DSC). The plasticizer can for example be chosen from the compounds defined in the book Handbook of Plasticizers edited by Georges Wypych. By way of example, mention may be made of dibutyl sebacate, dioctyl phthalate, Nn-butylsulfonamide, butylbenzenesulfonamide, polymeric polyesters and combinations thereof.

Advantageously, the internal polymeric sealing sheath comprises between 0% and 20% by weight of plasticizer and preferably between 1% and 10% by weight of plasticizer.

The internal polymeric sealing sheath can also include an impact modifier, which improves its behavior when cold. Thus, the composition can comprise up to 20% by weight, relative to the total weight of the composition, of an impact modifier, generally a polymer having a flexural modulus of less than 100 MPa measured according to standard ISO 178 of 2019. This impact modifier is, if necessary, chemically functionalized so as to be able to react with the polyamide and to form an alloy compatible with it. The impact modifier preferably consists of one or more polyolefins, some or all of these carrying a function chosen from carboxylic acid, carboxylic anhydride, epoxide functions and any other function capable of chemically reacting with polyamides. , typically with its amine chain ends (case of carboxylic acid, carboxylic anhydride) or its acid chain ends (case of epoxide, in particular glycidyl methacrylate). For example, the polyolefin is chosen from: a copolymer of ethylene and propylene with an elastomeric character (EPR), an ethylene-butene copolymer (EBR), an ethylene-octene copolymer (EOR), an ethylene-propylene-diene copolymer with elastomeric character (EPDM), a styrene-butadiene copolymer (SBR) and an ethylene / (meth) acrylate copolymer.

The internal polymeric sealing sheath comprises between 0% and 20% impact modifier and preferably between 1% and 10% impact modifier.

The internal polymeric sealing sheath comprising the polyamide as defined above can comprise one or more other additives, such as antioxidant, anti-UV, reinforcing filler, processing aid, heat stabilizer (for example a stabilizer of the BRUGGOLEN® H range from Brüggemann), hydrolysis retarder, nucleating agent (for example BRUGGOLEN® TP-P1401 from Brüggemann) and other fillers usually used in thermoplastics.

Typically, the internal polymeric sealing sheath consists of:

- 50 to 100% by weight of polyamide as defined above,

- 0 to 20% by weight of plasticizer,

- 0 to 20% by weight of impact modifier,

- 0 to 10% by weight of additives.

The inner polymeric sealant sheath is the single polymeric layer within the metallic reinforcement layer. The only polymeric layer within the at least one metallic reinforcement layer is the internal polymeric sealant sheath. On the other hand, the pipe may include one or more additional polymeric layer (s) on the outside of the metallic reinforcement layer.

The internal polymeric sealing sheath is single-layer, which excludes the internal polymeric multi-layer sealing sheaths, and that the layers are not bonded together or bonded together, in particular by an adhesive or because they were formed by coextrusion. A single layer rather than two or more makes it possible to avoid the accumulation of gas between the layers, and therefore the degradation by blistering phenomenon of the internal polymeric sealing sheath, for example in the event of sudden voluntary or involuntary depressurization of the underwater driving.

The internal polymeric sealing sheath is generally susceptible to contact with hydrocarbons. By "internal polymeric sealing sheath capable of being in contact with the hydrocarbons" is meant that the sheath or the layer comes into contact with the hydrocarbons when the pipe is put into service. Thus, the pipe does not include an internal tubular layer (i.e. an oil-tight layer) which would oppose contact between the oil and the cladding or layer. Typically, the pipe according to the invention does not include a polymeric tubular layer coated with the internal sealing polymeric sheath or a hydrocarbon-tight metal tube (a metal casing is not such a metal tube, because it does not is not tight against hydrocarbons).

The underwater pipe according to the invention is flexible. Generally, its metallic reinforcement layer consists of a long pitch winding of at least one metallic wire with non-contiguous turns, typically a tensile armor ply.

The flexible pipe typically comprises, from the outside to the inside of the pipe:

- at least one layer of tensile armor as a metallic reinforcement layer (generally two),

- the single-layer internal polymeric sealing sheath defined above,

- possibly a metal frame.

If the pipe includes a metal carcass, it is said to have a non-smooth passage ("rough-bore" in English). If the pipe is free of metal carcass, it is said to have a smooth passage ("smooth-bore" in English).

The main function of the metal carcass is to take up the radial forces directed from the outside to the inside of the pipe in order to avoid the collapse of all or part of the pipe under the pipe. effect of these efforts. These forces are linked in particular to the hydrostatic pressure exerted by the sea water when the flexible pipe is submerged. Thus, the hydrostatic pressure can reach a very high level when the pipe is submerged to great depth, for example 200 bar when the pipe is submerged to a depth of 2000 m, so that it is often essential to equip the flexible pipe. of a metal frame.

When the flexible pipe includes an outer polymeric sheath, the metal casing also has the function of preventing the collapse of the internal polymeric sealing sheath during rapid decompression of a flexible pipe that has transported hydrocarbons. This is because the gases contained in the hydrocarbons diffuse slowly through the internal polymeric sealing sheath and are partially trapped in the annular space between the internal polymeric sealing sheath and the outer polymeric sheath. As a result, during a production stoppage causing rapid decompression of the interior of the flexible pipe, the pressure prevailing in this annular space can temporarily become significantly greater than the pressure prevailing inside the pipe, which in turn the absence of a metal carcass would lead to the collapse of the internal polymeric sealing sheath.

Therefore, generally, for the transport of hydrocarbons, a pipe comprising a metal frame is preferred, while a pipe free from a metal frame will be suitable for the transport of water and / or water vapor under pressure. In addition, when the pipe is intended both to transport hydrocarbons and to be submerged to great depth, then the metal casing becomes essential in most applications.

The metal frame is made up of longitudinal elements helically wound at a short pitch. These longitudinal elements are strips or stainless steel wires arranged in turns stapled to each other. Advantageously, the metal carcass is produced by profiling an S-shaped strip and then winding it in a helix so as to staple the adjacent turns together.

In the present application, the notion of short-pitch winding designates any helical winding at a helix angle close to 90 °, typically between 75 ° and 90 °. The concept of long-pitch winding covers helix angles of less than 60 °, typically between 20 ° and 60 ° for the plies of armor.

The tensile armor plies consist of metal or composite material wires wound in long pitches and their main function is to take up the axial forces linked on the one hand to the internal pressure prevailing inside the flexible pipe and on the other hand to the weight of the flexible pipe, in particular when it is suspended. The presence of an additional metallic reinforcing layer intended to take up the radial forces linked to the internal pressure, a layer in particular called a "pressure vault", is not essential since the helix angles of the wires constituting the layers of The tensile armors are close to 55 °. In fact, this particular helix angle gives the tensile armor plies the ability to take, in addition to the axial forces, the radial forces exerted on the flexible pipe and directed from the inside to the outside of the pipe.

Preferably and especially for applications at great depth, in addition to the tensile armor plies, the flexible pipe comprises a pressure vault interposed between the internal polymeric sealing sheath and the tensile armor plies. In such a case, the radial forces exerted on the flexible pipe, in particular the radial forces directed from the inside to the outside of the pipe are taken up by the pressure vault in order to prevent the bursting of the internal polymeric sheath under the effect of the pressure inside the pipe. The pressure vault is made up of longitudinal elements wound in short pitch, for example metal wires of the shape Z (zeta), C, T (teta), U, K or X arranged in turns stapled to each other.

Advantageously and in particular depending on the grade of the metallic material constituting the tensile armor plies and of the possible pressure vault, the flexible pipe may include an external sealing polymeric sheath to prevent sea water from entering the breast. flexible pipe. This makes it possible in particular to protect the tensile armor layers from seawater and therefore prevent the phenomenon of corrosion by seawater.

Typically, driving includes, from the outside to the inside:

- an external polymeric sealing sheath,

- at least one layer of tensile armor as a metallic reinforcement layer,

- possibly a pressure vault,

- the single-layer internal polymeric sealing sheath as defined above,

- possibly a metal frame.

The nature, number, sizing and organization of the layers constituting the flexible pipes are essentially linked to their conditions of use and installation. The pipes may include additional layers to those mentioned above.

Advantageously, the flexible pipe is of the unbound type, that is to say that its reinforcing layers, such as the ply (s) of tensile armor and / or the pressure vault, are unbound. to the adjacent polymeric layer (s), such as the internal sealing polymeric sheath and / or the external sealing polymeric sheath and / or any tubular polymeric layer making up the flexible pipe. By “unbound” is meant that the reinforcing layers are free to move relative to the polymeric layers. Typically, the reinforcing layers of the flexible pipe are not embedded in a polymeric or elastomeric sheath. Likewise, there is preferably no adhesive between the reinforcing layers and the adjacent polymeric layer (s).

Flexible pipes can be used at great depths, typically up to 3000 meters deep. They allow the transport of fluids, in particular hydrocarbons, having a temperature typically reaching 130 ° C and which can even exceed 150 ° C and an internal pressure which can reach 1000 bars, or even 1500 bars.

The internal polymeric sealing sheath of the flexible pipe is typically tubular, generally has a diameter of 50 mm to 600 mm, preferably 50 to 400 mm, and / or a thickness of 1 mm to 150 mm, preferably 4 to 15 mm and / or a length of 1 m to 10 km.

According to a second object, the invention relates to a method for preparing the underwater pipe defined above, comprising the following steps:

a) extrusion to form the internal polymeric single-layer sealing sheath comprising the polyamide as defined above, the extrusion optionally being carried out on another layer,

b) assembly of the internal polymeric sealing sheath obtained in step a) with the metallic reinforcement layer, typically at least one ply of tensile armor (generally two plies of armor).

Extrusion step a) can be carried out by any method known to those skilled in the art, for example using a single-screw or twin-screw extruder.

A polymeric matrix comprising a polyamide as defined above can easily be extruded. When the internal polymeric sealing sheath comprises several polymers, the mixing of the two polymers can be carried out before or during the extrusion.

If the extrusion of step a) is not carried out on a carcass, but independently, the flexible pipe obtained is smooth bore.

If the extrusion of step a) is carried out on a carcass, the flexible pipe obtained has a non-smooth passage ("Rough bore" in English).

When the flexible pipe comprises other layers, the method comprises step b) of assembling the internal polymeric sealing sheath obtained during step a) with the other layers to form the flexible submarine pipe such as than the pressure vault and / or the outer polymeric sealing sheath.

The layers are thus assembled to form a flexible submarine pipe of the unbonded type, as described in the normative documents published by the American Petroleum Institute (API), API 17J and API RP 17B. .

According to a third object, the invention relates to an underwater pipe capable of being obtained by the aforementioned method.

According to a fourth object, the invention relates to the use of the aforementioned underwater pipe for the transport of hydrocarbons and / or gas.

The underwater pipe according to the invention is suitable for transporting gas, typically CO ₂ , in particular with a view to its reinjection into the underwater reservoir from which the hydrocarbons are extracted.

According to a fifth object, the invention relates to the use of a polyamide as defined above, in an internal polymeric single-layer sealing sheath of an underwater pipe intended for the transport of hydrocarbons and / or of gas and comprising a metallic reinforcing layer, to improve the resistance to stress corrosion of said subsea pipe. The embodiments described above are of course applicable.

According to a sixth object, the invention relates to a process for extracting hydrocarbons comprising:

- the extraction of a mixture of hydrocarbons and CO ₂ from an underwater deposit,

- the separation of hydrocarbons and CO ₂ ,

- the transport of at least part of the _{separated CO 2} to said underwater deposit in the pipe as defined above,

- the reinjection of the CO ₂ transported in said underwater deposit.

This process advantageously makes it possible to reduce CO ₂ emissions during extraction, and generally to increase the quantity of hydrocarbons which can be extracted from the underwater deposit.

The embodiments described above are of course applicable.

Other features and advantages of the invention will become apparent on reading the description given below of particular embodiments of the invention, given as an indication but not limited to, with reference to the single figure.

FIG. 1 is a partial schematic perspective view of a flexible pipe according to the invention. It illustrates a pipe in accordance with the invention comprising, from the outside to the inside:

- an external polymeric sealing sheath 10,

- an external layer of tensile armor 12,

- an internal layer of tensile armor 14 wound in the opposite direction of the external layer 12,

- a pressure vault 18 for taking up the radial forces generated by the pressure of the hydrocarbons or gases transported,

- an internal polymeric sealing sheath 20, and

- an internal carcass 22 for taking up the radial crushing forces,

wherein the internal polymeric sealing sheath 20 comprises a polyamide as defined above.

Due to the presence of the internal carcass 22, this pipe is said to have a non-smooth passage ("rough bore" in English). The invention could also be applied to a so-called smooth-bore pipe, not comprising an internal carcass.

Likewise, it would not be outside the scope of the present invention to eliminate the pressure vault 18, provided that the helix angles of the wires constituting the armor plies 12, 14 are close to 55 ° and in the opposite direction.

The armor plies 12, 14 are obtained by long-pitch winding of a set of wires made of metallic or composite material, of generally substantially rectangular section. The invention would also apply if these threads had a section of circular or complex geometry, of the self-stapled T type for example. In Figure 1, only two layers of armor 12 and 14 are shown, but the pipe could also include one or more additional pairs of armor. The armor ply 12 is said to be external because it is here the last, starting from the inside of the pipe, before the external sealing sheath 10.

The flexible pipe can also include layers not shown in Figure 1, such as:

- a retaining layer between the outer polymeric sheath 10 and the tensile armor plies 12 and 14, or between two tensile armor plies,

- one or more anti-wear layers ("anti-wear layer" in English) in polymeric material in contact either with the internal face of the aforementioned retaining layer, or with its external face, or with both faces, this anti-wear layer -wear to prevent the retaining layer from wearing out on contact with metal armor. The anti-wear layers, which are well known to those skilled in the art, are generally produced by helical winding of one or more tapes obtained by extrusion of a polymeric material based on polyamide, on polyolefins, or on PVDF (" polyvinylidene fluoride "in English). Reference may also be made to document WO 2006/120320 which describes anti-wear layers consisting of polysulfone (PSU), polyethersulfone (PES), polyphenylsulfone (PPSU), polyetherimide (PEI), polytetrafluoroethylene (PTFE), polyetheretherketone (PEEK) ribbons. ) or polyphenylene sulfide (PPS).

EXAMPLE :

CO permeability tests₂ (100%; single gas) were carried out following the protocol described in paragraph 6.2.3.2. of API 17J of 2014, in the variant without successive pressurization-decompression cycles and with CO pressure₂of 40 bars.

The experimental conditions are specified in Table 1.

The samples tested were cut from an extruded strip prepared from PA9T Genestar ™ N1006D-H31 from Kuraray or PA11 Rilsan P40TL from Arkema. The tested samples had a thickness of 0.177 cm, and a tested area of 12.57 cm ² .

The permeability coefficients (Pe) of PA9T and PA11 with respect to CO ₂ having crossed the membrane were determined from measurements by gas chromatography (GC) using a VARIAN gas chromatograph, model GC 3800.

Polymer PA9T PA11 (comparative) Temperature
(° C) 40 60 100 40 60 100 Pe
(cm ² / s / bar) 9.57x10 ^-9 1.43x10 ^-8 4.80x10 ^-8 3.38x10 ^-8 6.68x10 ^-8 2.09x10 ^-7

Table 1: Results of CO _{2 permeability tests}

These results show that PA9T has a better CO ₂ barrier effect than PA11. An internal polymeric sealing sheath made of PA9T therefore allows less CO _{2 to} pass from the hydrocarbons transported, or from the gas transported when this is CO ₂ , to the layers more external to the internal sealing sheath, in particular towards the metallic reinforcement layer, than a PA11 sheath. A PA9T sheath thus makes it possible to improve the resistance to stress corrosion of the metallic reinforcement layer.

Claims (12)

Submarine pipe intended for the transport of hydrocarbons and / or gas comprising a metallic reinforcement layer around a single-layer internal polymeric sealing sheath comprising a semi-crystalline semi-aromatic polyamide including:
- at least 60% by moles of the units derived from diamines are derived from one or more diamines chosen from aliphatic, cycloaliphatic or alkylaromatic diamines, said diamines having a number of carbons from 8 to 22, and
- at least 65% by moles of the units derived from dicarboxylic acids are derived from one or more aromatic dicarboxylic acids,
the internal polymeric sealing sheath being the single polymeric layer inside the metallic reinforcement layer. A submarine pipe according to claim 1, wherein the at least 60 mole% of units derived from diamines of the semi-crystalline semi-aromatic polyamide are derived from one or more diamines having a carbon number of 10 to 22. A submarine pipe according to claim 1 or 2, wherein the semi-crystalline semi-aromatic polyamide has:
- a melting temperature according to ISO 11357-3 of 2018 of less than 330 ° C, in particular of less than 300 ° C, preferably of less than 280 ° C, and / or
- an elongation at break at 20 ° C according to ISO 527-2 of 2012 greater than 20%, preferably greater than 40%, preferably greater than 50%, and / or
- retention of breaking strength of at least 50% when aged 90 days at 100 ° C in water at pH 6 according to API TR 17TR2 of 2003, and / or
- resistance to the blistering phenomenon at a pressure of 500 bars of CO ₂ and a temperature of 100 ° C, the resistance to the blistering phenomenon being evaluated according to API 17J of 2014. Underwater pipe according to claim 1 or 3, in which the at least 60% by moles of units derived from diamines of the semi-crystalline semi-aromatic polyamide are derived from one or more diamines chosen from:
- linear aliphatic diamines of formula H ₂ N- (CH ₂ ) _a -NH ₂ , a being an integer from 8 to 22, preferably chosen from octanediamine (a = 8), nonanediamine (a = 9) , decanediamine (a = 10), undecanediamine (a = 11), dodecanediamine (a = 12), tridecanediamine (a = 13), tetradecanediamine (a = 14), hexadecanediamine (a = 16) , octadecanediamine (a = 18), eicosanediamine (a = 20), docosanediamine (a = 22) and diamines obtained from fatty acids;
- branched aliphatic diamines having a carbon number of 8 to 22, preferably chosen from 2,2,4-trimethyl-1,6-hexanediamine, 2,4,4-trimethyl-1,6-hexanediamine, 2 , 4-diethyl-1,6-hexanediamine, 2,2-dimethyl-heptanediamine, 2,3-dimethyl-heptanediamine, 2,4-dimethyl-heptanediamine, 2,5-dimethyl-heptanediamine, 2-methyl -1,8-octanediamine, 3-methyl-1,8-octanediamine, 4-methyl-1,8-octanediamine, 1,3-dimethyl-1,8-octanediamine, 1,4-dimethyl-1 , 8-octanediamine, 2,2-dimethyl-1,8-octanediamine, 2,4-dimethyl-1,8-octanediamine, 3,3-dimethyl-1,8-octanediamine, 3,4-dimethyl -1,8-octanediamine, 4,4-dimethyl-1,8-octanediamine, 4,5-dimethyl-1,8-octanediamine, 5-methyl-1,9-nonanediamine, 2-butyl-1 , 8-octanediamine and 3-butyl-1,8-octanediamine;
- cycloaliphatic diamines having a number of carbons from 8 to 22,
preferably chosen from cycloaliphatic diamines having a carbon number of 8 to 22 and comprising a ring, such as 1,3-cyclohexanedimethylamine, 1,4-cyclohexanedimethylamine, 5-amino-2,2,4-trimethyl-1 -cyclopentanemethylamine, 5-amino-1,3,3-trimethylcyclohexanemethylamine, bis (aminopropyl) piperazine or bis (aminoethyl) piperazine, or from cycloaliphatic diamines having a carbon number of 8 to 22 and comprising two rings, such as than the cycloaliphatic diamines corresponding to the following formula:

in which :
- R ₁ , R ₂ , R ₃ and R ₄ independently represent a group chosen from a hydrogen atom or an alkyl of 1 to 6 carbon atoms, and
- X represents either a single bond or a divalent group consisting of:
- a linear or branched aliphatic chain comprising from 1 to 10 carbon atoms, optionally substituted by cycloaliphatic or aromatic groups of 6 to 8 carbon atoms, or
- a cycloaliphatic group of 6 to 12 carbon atoms,
the two-ring cycloaliphatic diamines being particularly preferably chosen from bis (4-aminocyclohexyl) methane, bis (3-methyl-4-aminocyclohexyl) propane, bis (3,5-dialkyl-4-aminocyclohexyl) methane, bis (3,5-dialkyl-4-aminocyclohexyl) ethane, bis (3,5-dialkyl-4-aminocyclohexyl) propane, bis (3,5-dialkyl-4-aminocyclo-hexyl) butane, bis- (3-methyl-4-aminocyclohexyl) -methane (denoted BMACM, MACM or B), p-bis (aminocyclohexyl) -methane (PACM) and bis (aminocyclohexyl) propane (PACP) (2,2-bis (4 -aminocyclohexyl) propane); and
- Alkylaromatic diamines having a number of carbons from 8 to 22, such as 1,3-xylylenediamine, 1,4-xylylenediamine, 2,5-bis-aminoethyl-para-xylene. Underwater pipe according to one of the preceding claims, in which the at least 65% by moles of units derived from dicarboxylic acids of the semi-crystalline semi-aromatic polyamide are obtained from one or more dicarboxylic acids chosen from acid phthalic acid, terephthalic acid (T), isophthalic acid (I), naphthalenic diacid, 1,3-phenylenedioxydiacetic acid 1,4-phenylenedioxydiacetic acid, diphenic acid, 4,4 acid '-oxydibenzoic acid, diphenylmethane-4,4'-dicarboxylic acid, diphenylethane-4,4'-dicarboxylic acid, diphenylpropane-4,4'-dicarboxylic acid, diphenylsulfone-4,4'- dicarboxylic, 4,4'-biphenyldicarboxylic acid, especially phthalic acid, terephthalic acid, isophthalic acid and naphthalenic diacid. Underwater pipe according to one of claims 1 and 3 to 5, in which:
- the at least 60% by moles of units derived from diamines of the semi-crystalline semi-aromatic polyamide are derived from one or more diamines chosen from 1,3-xylylenediamine, 1,9-nonanediamine, 2- methyl-1,8-octanediamine, 1,12-dodecanediamine and 1,18 octa-decanediamine, preferably 1,9-nonanediamine and 2-methyl-1,8-octanediamine, and / or
- at least 65% by moles of units derived from dicarboxylic acids of the semi-crystalline semi-aromatic polyamide are obtained from one or more aromatic dicarboxylic acids chosen from phthalic acid, terephthalic acid and isophthalic acid, preferably terephthalic acid. Submarine pipe according to one of claims 1 and 3 to 6, wherein the semi-crystalline semi-aromatic polyamide is PA9T, PA12T, PA18T or a mixture thereof, preferably PA9T. Underwater pipe according to one of the preceding claims, comprising, from the outside to the inside:
- an external polymeric sealing sheath,
- at least one layer of tensile armor as a metallic reinforcement layer,
- possibly a pressure vault,
- the internal polymeric single-layer waterproofing sheath,
- possibly a metal frame. Process for preparing the submarine pipe according to any one of claims 1 to 7, comprising the following steps:
a) extrusion to form the internal single-layer sealing polymeric sheath comprising the semi-crystalline semi-aromatic polyamide as defined in claim 1, the extrusion optionally being carried out on another layer,
b) assembly of the internal polymeric sealing sheath obtained in step a) with the metallic reinforcement layer. Use of an underwater pipe according to any one of Claims 1 to 8 for the transport of hydrocarbons and / or gas, in particular CO ₂ . Hydrocarbon extraction process comprising:
- the extraction of a mixture of hydrocarbons and CO ₂ from an underwater deposit,
- the separation of hydrocarbons and CO ₂ ,
- the transport of at least part of the _{separated CO 2} to said underwater deposit in the pipe according to any one of claims 1 to 8,
- the reinjection of the CO ₂ transported in said underwater deposit. Use of a semi-crystalline semi-aromatic polyamide polyamide including:
- at least 60% by moles of the units derived from diamines are derived from one or more diamines chosen from aliphatic, cycloaliphatic or alkylaromatic diamines having a number of carbons from 8 to 22, and
- at least 65% by moles of the units derived from dicarboxylic acids are derived from one or more aromatic dicarboxylic acids,
in a single-layer internal polymeric sealing sheath of an underwater pipe intended for the transport of hydrocarbons and / or gas and comprising a metallic reinforcing layer, to improve the resistance to stress corrosion of said underwater pipe .